Part a) what do you know that will you set up the equation to solve this problem? part b) write the equation that allows you to solve for the height. part c) what is the height of the trapezoid (including units)

A) You know the formula for the area of a trapezoid is ...
  A = (1/2)(b₁ +b₂)×h

B) You are given the area and the lengths of the two bases. Substituting the given numbers into the formula will give you an equation for h.
  280 cm² = (1/2)(8 cm +20 cm)×h

C) Solving the equation of part B, we have
  280 cm² = (14 cm)×h
  280 cm²/(14 cm) = h . . . . . . . . divide by the coefficient of h
  20 cm = h . . . . . . . . . . . . . . . .. evaluate

The height of the trapezoid is 20 cm.